The tree-destroying emerald ash borer appears to be continuing its slow expansion within infected parts of New Hampshire, judging from traps placed around the state.
The flying beetles were caught in five of about 40 scented traps hung in counties where the ash borer had been previously found, said William Davidson, who coordinates the emerald ash borer program for the New Hampshire Division of Forests and Lands.
Borers were found for the first time in Goffstown and Pittsfield, he said.
“It seems like it’s not spreading that fast, it’s moving slower than it has. . . . Their natural range expansion without human transport is a couple miles a year. This is pretty consistent with that,” Davidson said.
The fact that beetles weren’t found by more of the traps is “definitely a good sign,” he said, adding, “but this is a notoriously difficult pest to detect.”
The purple traps, which look like box kites with a triangular cross-section, have scent and color to attract the beetles, and a sticky surface to hold them. The traps are not designed to reduce populations but only to monitor where the beetle exists.
Davidson said traps were placed inside New Hampshire’s quarantine zones, which constitute all of Merrimack, Hillsborough, Rockingham and Belknap counties. No hardwood firewood, ash wood products, or ash nursery stock can be moved out of those counties.
The U.S. Department of Agriculture has placed some ash borer traps outside of those areas, but it has not released results from those traps for 2016, to determine whether the beetle has spread into new regions of New England.
The metallic green beetle is native to Asia and was accidentally brought into the U.S. in the 1990s, probably in imported wood or packing material. It was found near Detroit in 2002 and has since spread over much of the U.S. In New Hampshire it was found first in Concord, in 2013.
Adult beetles lay eggs on the bark of ash trees. When the eggs hatch, the larvae bore into the bark and feed on tissues of the tree, disrupting the movement of nutrients and water within the tree, eventually causing its death. Some experts have predicted that most of North America’s ash trees are likely to die as a result of the beetle, which has no natural enemies on this continent.
(David Brooks can be reached at 369-3313, dbrooks@cmonitor.com or on Twitter @GraniteGeek.)
